Weird export noise after appending object
The reason for the noise are the other lights and objects in the scene that are placed inside the planet. That's probably not where they are supposed to be because they can't be seen, but they have impact on the rendering and cause more noise. If you move them to another scene or exclude them from rendering it will look just like before. If they are supposed to be placed there and remain visible, you will need to increase the render sample to reduce the noise or you could enable denoising in the view layer.

Disable rendering for problematic objects.



Problematic objects


Before


After